Field of the Invention
The present invention relates to a liquid ejection apparatus including a liquid supply unit supplying a liquid to a liquid ejection head including an ejection opening ejecting a liquid droplet and also relates to a liquid ejection method and a liquid ejection head.
Description of the Related Art
As a recent liquid ejection apparatus, there is known an inkjet printing apparatus which forms an image by ejecting a liquid including a color material or a liquid (hereinafter, referred to as ink) such as a treatment liquid for adjusting quality of an image to be printed. In the inkjet printing apparatus, a predetermined amount of a gas is normally dissolved in the ink inside a liquid ejection head or an ink passage connected to the liquid ejection head. In a case where the gas dissolved in the ink becomes bubbles and the bubbles grow inside the passage or the liquid ejection head, the flow of the ink is disturbed or the ink ejection performance from an ejection opening is degraded, whereby a defective image is obtained.
For this reason, a suction recovery operation is performed on the inkjet printing apparatus in order to remove bubbles mixed with the ink in such a manner that the ink is forcibly collected from the inside of a passage or an ejection opening of a printing head by a depressurization operation while the ejection opening of the liquid ejection head is covered by a cap. The suction recovery operation is performed at a predetermined time interval in consideration of the generation/growth of the bubbles after the precedent suction operation. In a case where the worst condition, involving the generation of bubbles of the ink, is supposed and the recovery operation interval is set to prevent an ejection failure even in such a condition, a problem arises in that an amount of wasted ink increases since the frequency of performing the suction recovery operation increases.
As a technology of solving such a problem, Japanese Patent Laid-Open No. 2013-22886 discloses a method of controlling a recovery operation on the basis of a gas amount inside a passage forming member before ink is charged into an ink passage and a balanced gas amount inside the passage forming member after the ink is charged into the ink passage.
However, even when a suction recovery process or the like is performed in a case where the printing head is first driven after the installation of the inkjet printing apparatus, there is a possibility that bubbles may remain while not being sufficiently removed from the printing head or the ink passage. Then, there is a high possibility that the remaining bubbles may grow due to permeation from resin and a formation from saturated ink. Further, there is a case in which the circulation of the ink in the ink passage is interrupted or the ejection of the ink from the ejection opening is suppressed by the growing bubbles. Particularly, since bubbles adsorbed to resin in a resin passage are formed in a case where the ink is charged for use from a dry initial state in which the ink is not charged, the bubbles are easily generated and expanded. For this reason, there is a possibility that the bubbles may remain even after the suction recovery process or the like.
Thus, even in the technology disclosed in Japanese Patent Laid-Open No. 2013-22886, there is a need to frequently perform the recovery operation at an initial stage in which many bubbles are formed from the passage. When the frequency of performing the recovery operation increases, a waste ink amount increases. Accordingly, a running cost caused by the consumption of the ink increases and the capacity of the waste ink tank needs to be increased.